PRODUCTION AND SECRETION OF TRANSFORMING GROWTH-FACTOR-BETA (TGF-BETA) BY THE HUMAN LACRIMAL GLAND

Purpose. Transforming growth factor beta (TGF-beta) isoforms 1 and 2 h ave recently been detected in stimulated human tear fluid. The purpose of this study was to determine if these TGF-beta s are produced and s ecreted by the lacrimal gland. Methods. To accomplish this, reverse tr anscriptase polymerase chain reaction (RT-PCR) was used to detect expr ession of TGF-beta 1 and TGF-beta 2 mRNAs in normal human and rabbit l acrimal gland biopsies. Northern blot analyses were used for comparing the relative levels of expression of these TGF-beta mRNAs in rabbit l acrimal glands. Human lacrimal gland biopsies were evaluated by immuno histochemistry for production of TGF-beta 1, TGF-beta 1 latency associ ated peptide (LAP), and TGF-beta 2 proteins. Supernatants of unstimula ted and carbachol-stimulated human lacrimal gland explant cultures wer e evaluated for secretion of TGF-beta 1 and TGF-beta 2 by ELISA. Resul ts. TGF-beta 1 and TGF-beta 2 mRNA expression was found in all human a nd rabbit lacrimal gland specimens by RT-PCR. A greater level of expre ssion of TGF-beta 1 than TGF-beta 2 mRNA in the rabbit lacrimal gland was noted by Northern blot. In human lacrimal gland biopsies, TGF-beta 1 and TGF-beta 1 LAP were detected in acinar and ductal epithelia by immunohistochemistry. TGF-beta 2 specific antibodies stained a small p ercentage of acinar and ductal epithelia, as well as material within t he lumens of tubulo-acinar complexes in one-third of these glands. TGF -beta 1 was detected in supernatants of human lacrimal gland explants, and the concentration of TGF-beta 1 increased by an average of 280% a fter carbachol-stimulation (p = 0.004). TGF-beta 2 could not be detect ed in unstimulated or stimulated human lacrimal gland explant supernat ants. Conclusions. The results of these experiments indicate that TGF- beta 1 and TGF-beta 2 are produced by and TGF-beta 1 is secreted by th e human lacrimal gland. They also suggest that the lacrimal gland may be one source of TGF-beta in human tear fluid.